Composite Airfoil Singlets for Turbomachinery Stress Reduction
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Solution Overview
Problem
Turbomachinery vane segments made from composite materials face high interlaminar tensile and compression stresses due to differential forces between pressure and suction sides, leading to negative stress margins and potential structural weaknesses.
Innovation Solution
A composite airfoil singlet design featuring an airfoil extending from a base to a tip, integrally formed with no more than one outer platform at the tip and/or one inner platform at the base, using parallel composite plies or woven fibers, with outer and inner curved sections and secured by integrally formed fastening plates and shanks, reducing interlaminar stresses through optimized structural integration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If composite vane segments are made from multiple CMC plies with branching into platforms, then the structural coverage and support are improved, but interlaminar tensile and compression stresses increase leading to negative stress margins
Solution Approach 1:
The vane is divided into separate airfoil and platform components that are assembled together using fastening plates and fasteners. This segmentation eliminates the need for plies to bend and branch into platforms, thereby removing the source of interlaminar stresses while maintaining structural support through the assembled configuration.
Solution Approach 2:
The airfoil and platform are merged into a single integrated component in this invention, eliminating the need for separate plies to branch into platforms. This integration removes the triangular areas where high interlaminar stresses occur, while the fastening system provides the necessary structural connection to the shroud.
2Reliability
If multiple CMC plies are used to form airfoil and platform sections, then comprehensive structural coverage is achieved, but device complexity increases due to triangular areas and stress management
Solution Approach 1:
The vane structure is segmented into distinct airfoil and platform components that are manufactured separately and then assembled. This eliminates the complex triangular ply configurations required when using monolithic composite structures, simplifying the manufacturing process while maintaining comprehensive structural coverage through the assembled components.
Solution Approach 2:
Fastening plates and fasteners serve as intermediary elements that connect the airfoil and platform components to each other and to the shroud. This intermediary connection system simplifies the overall structure by eliminating the need for complex integrated ply configurations, while still achieving comprehensive structural coverage and load transfer.
3Strength
If plies branch from airfoil into platforms in both directions, then platform support is provided, but interlaminar tensile and compression stresses create potential structural weaknesses
Solution Approach 1:
The platform is provided as a separate component rather than being formed by branching plies from the airfoil. This segmentation eliminates the triangular areas where plies bend and branch, which are the sources of high interlaminar tensile and compression stresses, thereby removing potential structural weaknesses while maintaining platform support through the assembled configuration.
Solution Approach 2:
The airfoil and platform are merged into a single integrated component manufactured as one piece, eliminating the need for plies to branch into the platform. This integration removes the source of interlaminar stresses and potential structural weaknesses, while the fastening system provides the necessary connection to the shroud for platform support.
Data Source
AI summary
Composite airfoil singlet, includes airfoil extending from base to tip of airfoil, integrally formed with no more than one outer platform at tip and/or no more than one inner platform at base. Parallel composite plies or woven fibers extend through airfoil and through outer and/or inner platforms. Outer and/or inner curved sections extend between outer and/or inner platforms and airfoil respectively. Assembly includes circular row of the composite airfoil singlets depending radially inwardly from and mounted to an outer shroud or casing. Outer and/or inner fasteners may secure outer and inner platforms to outer shroud or casing and an inner shroud respectively and include shanks extending substantially perpendicularly from outer and inner fastening plates though platform holes in outer and inner platforms and through outer and inner holes in outer shroud or casing and inner shroud respectively. Nuts are screwed on threaded ends of shanks.